High content pcbn compact including w-re binder

ABSTRACT

The present invention relates to tungsten-rhenium coated compounds, materials formed from tungsten-rhenium coated compounds, and to methods of forming the same. In embodiments, tungsten and rhenium are coated on ultra hard material particles to form coated ultra hard material particles, and the coated ultra hard material particles are sintered at high temperature and high pressure.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/530,311, the disclosure of which is incorporatedherein by reference in its entirety.

BACKGROUND

Various hard materials and methods of forming hard materials can be usedto form cutting tools as well as tools used for friction stir welding. Atool used for friction stir welding includes a hard metal pin that ismoved along the joint between two pieces to plasticize and weld the twopieces together. Because this process wears greatly on the tool, hardand strong materials are very desirable. As a result, hard metalcompounds and composites have been developed to improve wear resistance.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

Aspects of embodiments are generally directed to a method of forming amaterial, the method including: coating ultra hard material particleswith tungsten and rhenium to form coated ultra hard material particles;and sintering the coated ultra hard material particles at ultra hightemperature and high pressure (HPHT).

The coating may be performed by a method selected from the groupconsisting of chemical vapor deposition, electroless plating, physicalvapor deposition and combinations thereof.

In certain embodiments, the ultra hard material particles are greaterthan 80% of the volume of the material, and the tungsten and rhenium aretogether less than 20% of the volume of the material.

Coating the ultra hard material particles with tungsten and rhenium mayform an alloy of tungsten and rhenium.

In certain embodiments, the ultra hard material particles are coatedconcurrently with tungsten and rhenium.

In other embodiments, the ultra hard material particles are coatedindependently with tungsten and rhenium.

In one embodiment, coating the ultra hard material particles withtungsten and rhenium includes coating the ultra hard material particleswith tungsten before coating the ultra hard material particles withrhenium.

In another embodiment, coating the ultra hard material particles withtungsten and rhenium includes coating the ultra hard material particleswith rhenium before coating the ultra hard material particles withtungsten.

In another embodiment, the ultra hard material particles are coated withrepeated alternating layers of tungsten and rhenium.

The ultra hard material particles may have a particle size in a range ofabout 0.1 μm to about 100 μm.

Coating the ultra hard material particles with tungsten and rhenium mayform a coating having a thickness in a range of about 0.002 μm to about10 μm.

Coating the ultra hard material particles with tungsten and rhenium mayform a coating including tungsten in an amount in a range of about 50weight percent to about 95 weight percent based on the total weight ofthe coating.

Coating the ultra hard material particles with tungsten and rhenium mayform a coating including rhenium in an amount in a range of about 5weight percent to about 50 weight percent based on the total weight ofthe coating.

In certain embodiments, coating the ultra hard material particles withtungsten and rhenium forms a coating, and the coating further includesboron.

Boron may be present in the coating in an amount in a range of about 0.1atomic percent to about 20 atomic percent based on the total number ofatoms in the coating.

In one embodiment, coating the ultra hard material particles withtungsten and rhenium forms a coating, and the coating further includesaluminum.

For example, coating the ultra hard material particles with tungsten andrhenium may form a coating, and the coating may further include Al₂O₃.

In certain embodiments, sintering the coated ultra hard materialparticles includes forming a chemical bond between the ultra hardmaterial particles and at least one of the tungsten or rhenium.

The ultra hard material particles may include cubic boron nitride.

Additionally, sintering the cubic boron nitride may include forming achemical bond between at least a portion of the cubic boron nitride andat least one of the tungsten or rhenium.

In one embodiment, the temperature is in a range of about 1000° C. toabout 2300° C.

For example, the temperature may be about 1450° C.

In one embodiment, the pressure is in a range of about 20 kilobars toabout 75 kilobars.

In certain embodiments, the ultra hard material particles are partiallycoated with tungsten and rhenium.

For example, the ultra hard material particles may be coated withtungsten and rhenium to form a discontinuous coating.

In other embodiments, the ultra hard material particles are completelycoated with tungsten and rhenium.

For example, the ultra hard material particles may be coated withtungsten and rhenium to form a continuous coating.

Aspects of embodiments of the present invention are also generallydirected to a polycrystalline material including: a tungsten-rheniummatrix; and ultra hard material grains dispersed in the matrix andbonded to at least one of the tungsten or rhenium, the polycrystallinematerial having been formed by coating ultra hard material particleswith tungsten and rhenium to form coated ultra hard material particlesand sintering the coated ultra hard material particles at hightemperature and pressure.

The coating may be performed by a method selected from the groupconsisting of chemical vapor deposition, electroless plating, physicalvapor deposition and combinations thereof.

In certain embodiments, the ultra hard material grains are greater than80% of the volume of the polycrystalline material, and the tungsten andrhenium are together less than 20% of the volume of the polycrystallinematerial.

The ultra hard material grains may have a grain size in a range of about0.1 μm to about 100 μm.

In certain embodiments, at least a portion of the tungsten-rheniummatrix has a thickness of about 0.002 μm to about 10 μm.

The tungsten may be present in the tungsten-rhenium matrix in an amountin a range of about 50 weight percent to about 95 weight percent basedon the total weight of the tungsten-rhenium matrix.

The rhenium may be present in the tungsten-rhenium matrix in an amountin a range of about 5 weight percent to about 50 weight percent based onthe total weight of the tungsten-rhenium matrix.

In certain embodiments, the tungsten-rhenium matrix further includesboron.

For example, boron may be present in the tungsten-rhenium matrix in anamount of about 0.1 atomic percent to about 20 atomic percent based onthe total number of atoms in the tungsten-rhenium matrix.

The tungsten-rhenium matrix may further include aluminum.

The tungsten-rhenium matrix may further include Al₂O₃.

In certain embodiments, the ultra hard material grains include cubicboron nitride, and at least a portion of the cubic boron nitride ischemically bonded to a portion of the tungsten-rhenium matrix.

In certain embodiments, tungsten, rhenium and the ultra hard materialgrains define a polycrystalline ultra hard material layer, and thematerial further includes a substrate bonded to said polycrystallineultra hard material layer.

Aspects of embodiments of the present invention are also generallydirected to a polycrystalline material including: a tungsten-rheniummatrix; and ultra hard material grains dispersed in said matrix, theultra hard material grains being greater than 80% of the volume of thepolycrystalline material, and the tungsten and rhenium being togetherless than 20% of the volume of the polycrystalline material.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, together with the specification, illustrateembodiments of the present invention, and, together with thedescription, serve to explain the principles of the invention. The samenumbers are used to throughout the figures to reference like featuresand components.

FIG. 1 illustrates an example method for forming a material inaccordance with one or more embodiments.

FIG. 2 illustrates an example of a prophetic coated ultra hard materialparticle according to one or more embodiments.

FIG. 3 illustrates another example of a prophetic coated ultra hardmaterial particle according to one or more embodiments.

FIG. 4 illustrates another example of a prophetic coated ultra hardmaterial particle according to one or more embodiments.

FIG. 5 illustrates various components of an example device that canimplement a sintered ultra hard material according to one or moreembodiments.

FIG. 6 illustrates a sintered ultra hard material according to one ormore embodiments bonded onto a substrate.

DETAILED DESCRIPTION

In the following detailed description, only certain embodiments of thepresent invention are shown and described, by way of illustration. Asthose skilled in the art would recognize, the invention may be embodiedin many different forms and should not be construed as being limited tothe embodiments set forth herein. For example, many of the elementsdescribed herein may be replaced by any one of numerous equivalentalternatives, only some of which are disclosed in the specification.

The present invention relates generally to materials prepared fromtungsten-rhenium coated ultra hard material particles and moreparticularly to methods of forming the same at high temperatures andhigh pressures. According to embodiments, tungsten (W) and rhenium (Re)are coated on ultra hard material particles and sintered at highpressure and high temperature (HPHT sintering) to form a uniquematerial, rather than simply mixing tungsten and rhenium with an ultrahard material and sintering the mixture. The ultra hard material may becubic boron nitride (CBN), another suitable ultra hard material known inthe art, or a combination of these materials.

Ultra hard material compacts, for use in cutting tools as well as toolsused for friction stir welding, having a metallic binder phase have beenprepared by mixing (i.e., mechanically mixing) ultra hard materialpowders, such as cubic boron nitride (cBN) and refractory metal powdersand sintering the mixture. Such processes, however, result in sinteredmicrostructures that are not very uniform. Consequently, materialsproduced by such processes require a high volume percent of the binderphase (i.e., the metal powder) to achieve full densification of thematerial. That is, to achieve full densification of the material and acontinuous binder phase, the binder phase must be at least 20% orgreater of the volume of the material. As a result, the volume percentof ultra hard material in a material prepared from a mixture (i.e., aphysical mixture) of ultra hard material powders and metal powders islimited to less than about 80% of the volume of the material.Accordingly, methods of preparing materials from mixtures of ultra hardmaterial powders and metal powders cannot produce fully densifiedmaterials having an amount of ultra hard material of greater than 80% ofthe volume of the material and a binder phase of less than 20% of thevolume of the material.

Examples of hard materials also include cemented carbides, which includea carbide, such as tungsten carbide, bound with a binder such as cobalt,nickel or rhenium. Carbide-based hard materials have been produced withrhenium as the only binder, using conventional sintering methods.Tungsten-rhenium alloys have also been produced with standard arcmelting or sintering methods. Such tungsten-rhenium alloys can be usedfor high temperature tools and instruments. However, materials withimproved wear resistance are desired for use in tools such as cuttingtools and friction stir welding tools.

According to embodiments of the present invention, a method of forming amaterial includes coating ultra hard material particles with tungstenand rhenium to form coated ultra hard material particles (as shown in100 of FIG. 1), and sintering the coated ultra hard material particlesat high temperature and high pressure (as shown in 200 of FIG. 1).Coating the ultra hard material particles with tungsten and rheniumbefore sintering should result in a more uniform sinteredpolycrystalline ultra hard material microstructure, which should allowthe preparation of materials having a lower volume percent of binderphase (e.g., tungsten and rhenium) in the material than was previouslypossible. As such, materials prepared according to embodiments of thepresent invention may have a higher volume percent of ultra hardmaterial grains or crystals (formed from the ultra hard materialparticles) than was possible with previous methods, while still forminga dense compact. Specifically, according to an embodiment of the presentinvention, the ultra hard material grains are greater than 80% of thevolume of the material, and the tungsten and rhenium are together lessthan 20% of the volume of the material. The resulting material shouldhave both high hardness, due to the high volume percent of ultra hardmaterial particles, and toughness, due to the presence of the uniformand continuous refractory metal network (i.e., the tungsten-rheniummatrix formed from the tungsten and rhenium coating). Additionally, bycoating the ultra hard material particles with tungsten and rheniumprior to sintering, the material of embodiments of the present inventionmay be sintered at a relatively lower temperature than is required forcertain methods of forming other, similar materials.

As used herein, the phrase “coated ultra hard material particles” refersto ultra hard material particles, such as cBN, that have a strongerinteraction between the particles and the tungsten and rhenium coatingthan that which would result from physically mixing ultra hard materialparticles, tungsten and rhenium. That is, the van der Waalsinteractions, or other interactions, between physically mixed ultra hardmaterial particles and tungsten-rhenium are insufficient to give rise to“coated ultra hard material particles” as the phrase is used herein.Rather, tungsten and rhenium are coated on the ultra hard materialparticles by any suitable coating process. For example, according to anembodiment of the present invention, the coating may be performed by amethod such as chemical vapor deposition, electroless plating, physicalvapor deposition or combinations thereof. In particular, the coating maybe performed by an electroless plating method, such as described in U.S.Pat. No. 6,797,312, the entire contents of which are herein incorporatedby reference. For example, the coating may be performed by contactingthe ultra hard material particles with an electroless plating solutionto form a coating, such as a tungsten-rhenium alloy coating, on asurface of the ultra hard material particles. The ultra hard materialparticles may be cleaned, rinsed and/or contacted with a catalyst priorto contacting the electroless plating solution.

A continuous or discontinuous layer of tungsten and rhenium may beformed by the coating, and the layer may be uniform. Specifically, theultra hard material particles may be partially coated with tungsten andrhenium, or the ultra hard material particles may be completely coatedwith tungsten and rhenium.

In certain embodiments, coating the ultra hard material particles withtungsten and rhenium forms a coating that includes tungsten and rhenium.For example, FIG. 2 is a schematic representation of a prophetic coatedultra hard material particle 10, which includes an ultra hard materialparticle 20 and a tungsten and rhenium coating 30. As can be seen inFIG. 2, the ultra hard material particle 20 is coated (or completelycoated) with the tungsten and rhenium to form a continuous coating 30.In another embodiment (shown in FIG. 3), the ultra hard materialparticle 20 is coated (or partially coated) with the tungsten andrhenium to form a discontinuous coating 30. According to any of theembodiments of the present invention, the coating 30 may includetungsten and rhenium as a mixture, or it may include tungsten andrhenium as an alloy. In certain embodiments, the coating 30 is formed bycoating tungsten and rhenium concurrently. In other embodiments, thecoating 30 is formed by coating tungsten and rhenium independently. Thecoating process may be repeated several times to form the coated ultrahard material particles.

According to still another embodiment of the present invention, thetungsten and rhenium coating may be present as two or more distinctlayers. For example, FIG. 4 is a schematic representation of a propheticcoated ultra hard material particle 10, which includes an ultra hardmaterial particle 10, a first coating layer 40 and a second coatinglayer 50. Tungsten and rhenium may be independently coated (e.g.,deposited) to form the first and second coating layers. For example, incertain embodiments, the ultra hard material particles may be coatedwith tungsten before coating the ultra hard material particles withrhenium. According to this embodiment, tungsten may be coated (e.g.,deposited) to form the first coating layer 40, and rhenium may besubsequently coated (e.g., deposited) to form the second coating layer50. In another embodiment, the ultra hard material particles may becoated with rhenium before coating the ultra hard material particleswith tungsten. According to that embodiment, rhenium may be used to formthe first coating layer 40, and tungsten may be used to form the secondcoating layer 50. In any of the above embodiments, the coating processmay be repeated several times to form the coated ultra hard materialparticles.

The thickness of the tungsten-rhenium coating is a function of thevolume percent of the ultra hard material particles in the material, thevolume percent of the tungsten and rhenium (i.e., the coating) in thematerial, and the particle diameter of the ultra hard materialparticles. In embodiments of the present invention, the thickness of thetungsten-rhenium coating can be estimated according to the followingFormula:

${{{coating}\mspace{14mu} {thickness}} = {\left( {\sqrt[3]{1 + \frac{V_{W - {Re}}}{V_{UHM}}} - 1} \right) \times \frac{D_{UHM}}{2}}},$

wherein V_(UHM) is the volume percent of the ultra hard materialparticles in the material, V_(W-Re) is the volume percent of tungstenand rhenium in the material, and D_(UHM) is the particles diameter (μm)of the ultra hard material particles. For example, in certainembodiments, the ultra hard material particles include cubic boronnitride (cBN), and the thickness of the tungsten-rhenium coating can becalculated according to the following Formula:

${{{coating}\mspace{14mu} {thickness}} = {\left( {\sqrt[3]{1 + \frac{V_{W - {Re}}}{V_{cBN}}} - 1} \right) \times \frac{D_{cBN}}{2}}},$

wherein V_(cBN) is the volume percent of cBN particles in the material,V_(W-Re) is the volume percent of tungsten and rhenium in the material,and D_(cBN) is the particle diameter (μm) of the cBN particles. In theabove Formulae, each of the ultra hard material particles or cBNparticles is assumed to have an approximately spherical shape and thetungsten-rhenium coating is assumed to be an approximately sphericalshell coating the approximately spherical particles. Thus, thecalculated coating thicknesses are approximate, and the actual coatingthicknesses may vary. In practice, the ultra hard material particles arenot limited to spherical or approximately spherical shapes, but insteadcan have any shape. Table 1 shows the cBN particle diameter andcorresponding tungsten-rhenium coating thickness estimated according tothe above Formulae for materials having 80 volume percent cBN particles,85 volume percent cBN particles, and 90 volume percent cBN particles inthe material.

TABLE 1 80 volume 85 volume 90 volume percent cBN percent cBN percentcBN cBN cBN cBN particle Coating particle Coating particle Coatingdiameter thickness diameter thickness diameter thickness (μm) (μm) (μm)(μm) (μm) (μm) 2.0 0.08 2.0 0.06 2.0 0.04 4.0 0.15 4.0 0.11 4.0 0.07 6.00.23 6.0 0.17 6.0 0.11 8.0 0.31 8.0 0.22 8.0 0.14 10.0 0.39 10.0 0.2810.0 0.18 16.0 0.62 16.0 0.45 16.0 0.29

In certain embodiments, the ultra hard material particles have aparticle size in a range of about 0.1 μm to about 100 μm. The ultra hardmaterial particles may have a bimodal particle size (i.e., two distinctparticle size populations) or the ultra hard material particles may havea broad distribution of particle sizes. In certain embodiments, coatingthe ultra hard material particles with tungsten and rhenium forms acoating having a thickness in a range of about 0.002 μm to about 4 μm.

In an embodiment, a material is formed from the tungsten and rheniumcoated ultra hard material particles as follows. The tungsten andrhenium coated ultra hard material particles are introduced into anenclosure, known as a “can,” which may be formed from niobium ormolybdenum. The can with the coated ultra hard material particles isthen placed in a press and subjected to high pressure and hightemperature conditions. The elevated pressure and temperature conditionsare maintained for a time sufficient to sinter the materials. After thesintering process, the enclosure and its contents are cooled and thepressure is reduced to ambient conditions.

In embodiments of the present invention, the material is formed bycoating ultra hard material particles with tungsten and rhenium, andHPHT sintering, as contrasted from other sintering processes. In HPHTsintering, the sintering process is conducted at very elevated pressureand temperature. In some embodiments, the pressure is within the rangefrom about 20 to about 75 kilobars, and the temperature is within therange from about 1000° C. to about 2300° C. For example, in certainembodiments, the ultra hard material particles are coated, and then thecoated ultra hard material particles are pressed at temperatures, suchas, about 1200° C., 1400° C., or 1450° C. As explained more fully below,HPHT sintering should result in chemical bonding between the sinteredmaterials, rather than simply fixing the hard particles in place bymelting or plastically the binder around the hard particles. Forexample, HPHT sintering the coated ultra hard material particles mayinclude forming a chemical bond between the ultra hard materialparticles, such as cubic boron nitride particles, and at least one ofthe tungsten or rhenium.

The relative percentages of tungsten and rhenium coated on the ultrahard material particles can vary depending on the desired materialproperties. For example, coating the ultra hard material particles withtungsten and rhenium may form a coating including tungsten in an amountin a range of about 50 weight percent to about 95 weight percent basedon the total weight of the coating. In one embodiment, the coating mayinclude tungsten in an amount of about 75 weight percent or higher. Asanother example, coating the ultra hard material particles with tungstenand rhenium may form a coating including rhenium in an amount in a rangeof about 5 weight percent to about 50 weight percent based on the totalweight of the coating. In one embodiment, the coating may includerhenium in an amount of about 25 weight percent or lower.

In one embodiment, ultra hard material particles are coated withtungsten and rhenium to form coated ultra hard material particles havinguniform microstructure. The tungsten, rhenium and ultra hard materialparticles are sintered at high temperature and high pressure to form apolycrystalline ultra hard material. The ultra hard material particlesmay include cubic boron nitride (CBN) particles or other suitable ultrahard material particles. In the resulting tungsten-rhenium matrix formedby HPHT sintering, the rhenium should provide improved toughness andstrength at high temperature. The tungsten-rhenium matrix should have ahigher recrystallization temperature than either tungsten or rheniumalone, leading to improved high temperature performance. For example,using the material to manufacture a friction stir welding tool shouldresult in a tool that can weld across a longer distance as compared withfriction stir welding tools formed with traditional W—Re alloys,tungsten carbides or physical mixtures of tungsten, rhenium, and anultra hard material. The present inventors expect that the improved hightemperature performance of a material according to embodiments of thepresent invention will provide improved wear resistance. The HPHTsintering should also create a material with higher density compared toconventional sintering.

In embodiments, the ultra hard material particles are coated with thetungsten and rhenium with the relative proportions being greater than80% ultra hard material particles and less than 20% W—Re by volume. TheW—Re proportions may be 25% or lower Re. However, this ratio is veryflexible, and the percentage of Re compared to W may be varied from 50%to 5%. In addition, the percentage of ultra hard material particles maybe varied from 50% to 95%. The coated ultra hard material particles arethen sintered at high temperature and high pressure, as described above,forming a polycrystalline ultra hard material. The resultingpolycrystalline material includes the polycrystalline ultra hardmaterial bound by the tungsten-rhenium binder alloy.

Additionally, the tungsten and rhenium coating or the tungsten-rheniummatrix formed from the coating may include additional additives. Forexample, the coating may further include boron, such as a coating thatincludes boron in an amount in a range of about 0.1 atomic percent toabout 20 atomic percent based on the total number of atoms in thecoating. In one embodiment, the material includes 1% aluminum by weightbased on the total weight of the material. For example, the coating mayinclude Al₂O₃.

The present inventors expect that materials according to embodiments ofthe present invention should have high strength. In particular, thepresent inventors expect materials prepared according to embodiments ofthe present invention should have better strength and hardness thanmaterials prepared from physical mixtures of ultra hard material powdersand metal powders. Possible explanations for the expected high strengthinclude improved sintering of the W—Re matrix, improved bonding at theinterface between the W—Re and ultra hard material particles throughreactive sintering, improved alloying of the W—Re matrix, and theformation of aluminum oxide (Al₂O₃). The present inventors also expectthat the higher volume percent of ultra hard material particles in thematerial will improve the wear resistance of the sintered parts, whilethe high-melting point W—Re binder will maintain the strength andtoughness at high temperature operations. The sintered material may beused for various tools, such as friction stir welding (FSW) tools. AnFSW tool 62 of an FSW apparatus 60 is shown in FIG. 5. An FSW tool 61,as shown in FIG. 5, mechanically joins two metallic materials 64, 66 byplastic deforming and mixing the materials being joined at sub-meltingtemperatures. The FSW tool is driven to rotate by an FSW spindle 60which “stirs” the materials to be joined. The FSW tool has a base 68from which extends a pin 70 which penetrates the materials to be joinedand does the stirring.

A material according to embodiments of the present invention could alsobe bonded onto a substrate 80, such as tungsten carbide, to form acutting layer 82 of a cutting element 84, as shown in FIG. 6. Forexample, the material could be bonded (e.g., welded or brazed) to asubstrate after the material has been sintered. In another embodiment,prior to sintering, the material and the substrate could be placed inthe can together and sintered, thereby bonding the material to thesubstrate.

Unlike materials produced with conventional sintering or cementing, theabove-described HPHT materials should form a solid chemical bond betweenthe matrix and the ultra hard material particles (e.g., cubic boronnitride particles). For example, the boron from the cubic boron nitrideshould react with the rhenium from the W—Re matrix to form rheniumboride, creating a strong bond between the matrix and the ultra hardmaterial particles. This cubic boron nitride material should not simplyproduce a material with hard particles dispersed inside a melted matrix,but instead should produce a material with chemical bonding between theultra hard material particles and the matrix. The bonding mechanismbetween the ultra hard material particles and binder may vary dependingon the ultra hard material used.

Moreover, materials according to embodiments of the present inventionshould have more uniform microstructure than materials prepared fromphysical mixtures of ultra hard materials, tungsten and rhenium. Bycoating tungsten and rhenium on ultra hard material particles, materialsaccording to embodiments of the present invention should be capable ofbeing prepared at relatively lower temperatures and the material shouldbe capable of being prepared having a higher volume percent of ultrahard material particles than could be achieved using physical mixturesof ultra hard material, tungsten and rhenium. While the presentinvention has been described in connection with certain embodiments, itis to be understood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims, and equivalents thereof.

What is claimed is:
 1. A method of forming a material, comprising:coating ultra hard material particles with tungsten and rhenium to formcoated ultra hard material particles; and sintering the coated ultrahard material particles at high temperature and high pressure.
 2. Themethod of claim 1, wherein the coating is performed by a method selectedfrom the group consisting of chemical vapor deposition, electrolessplating, physical vapor deposition, and combinations thereof.
 3. Themethod of claim 1, wherein the ultra hard material particles are greaterthan 80% of the volume of the material, and the tungsten and rhenium aretogether less than 20% of the volume of the material.
 4. The method ofclaim 1, wherein coating the ultra hard material particles with tungstenand rhenium forms an alloy of tungsten and rhenium.
 5. The method ofclaim 1, wherein tungsten and rhenium are coated concurrently.
 6. Themethod of claim 1, wherein tungsten and rhenium are coatedindependently.
 7. The method of claim 1, wherein coating the ultra hardmaterial particles with tungsten and rhenium forms a coating, and thecoating further comprises boron.
 8. The method of claim 1, whereincoating the ultra hard material particles with tungsten and rheniumforms a coating, and the coating further comprises aluminum.
 9. Themethod of claim 1, wherein sintering the coated ultra hard materialparticles comprises forming a chemical bond between the ultra hardmaterial particles and at least one of the tungsten or rhenium.
 10. Themethod of claim 1, wherein the ultra hard material particles comprisecubic boron nitride.
 11. The method of claim 1, wherein coating theultra hard material particles with tungsten and rhenium forms a coating,and the ultra hard material particles have a stronger interaction withthe coating than that which would result from physically mixing ultrahard material particles, tungsten and rhenium.
 12. The method of claim1, wherein the temperature is in a range of about 1000° C. to about2300° C.
 13. The method of claim 1, wherein the pressure is in a rangeof about 20 kilobars to about 75 kilobars.
 14. A polycrystallinematerial comprising: a tungsten-rhenium matrix; and ultra hard materialgrains dispersed in said matrix and bonded to at least one of thetungsten or rhenium, the polycrystalline material formed by coatingultra hard material particles with tungsten and rhenium to form coatedultra hard material particles and sintering the coated ultra hardmaterial particles at high temperature and pressure.
 15. Thepolycrystalline material of claim 14, wherein the ultra hard materialgrains are greater than 80% of the volume of the polycrystallinematerial, and the tungsten and rhenium are together less than 20% of thevolume of the polycrystalline material.
 16. The polycrystalline materialof claim 14, wherein the ultra hard material grains have a grain size ina range of about 0.1 μm to about 100 μm.
 17. The polycrystallinematerial of claim 14, wherein at least a portion of the tungsten-rheniummatrix has a thickness of about 0.002 μm to about 10 μm.
 18. Thepolycrystalline material of claim 14, wherein the ultra hard materialgrains comprise cubic boron nitride, and at least a portion of the cubicboron nitride is chemically bonded to a portion of the tungsten-rheniummatrix.
 19. The polycrystalline material of claim 14, wherein saidtungsten, rhenium and the ultra hard material grains define apolycrystalline ultra hard material layer, and the polycrystallinematerial further comprises a substrate bonded to said polycrystallineultra hard material layer.
 20. A polycrystalline material comprising: atungsten-rhenium matrix; and ultra hard material grains dispersed insaid matrix, the ultra hard material grains being greater than 80% ofthe volume of the polycrystalline material, and the tungsten and rheniumbeing together less than 20% of the volume of the polycrystallinematerial.